This invention generally relates to vehicle brake shoe assemblies where the web members and the brake shoe table are joined by a linear friction welding process.
Modern vehicles require precisely made brake shoe assemblies. Typically, brake shoes are made with a multiple step, relatively complex and expensive process. For example, the brake shoe table is roll formed to a prescribed curvature. Two webs are then aligned and projection welded to the table. After the webs are joined to the table, appropriate slots are cut or formed in the webs to make the brake shoe workable with the remainder of a brake assembly. The slots in the webs must be heat treated to achieve a high hardness. Heat treating the webs is more difficult after they have been joined to the table. Previously, however, it was not possible to perform the hardening process before joining the webs to the table because of the requirements of providing a precisely aligned set of slots in the webs, which would be distorted during the typical process of joining the webs to the table.
There are several disadvantages and drawbacks to the usual method of assembling a brake shoe. Performing the heat treatment step after assembling the webs to the shoe as discussed above is less controlled than is desirable and adds an expensive step to the assembly process. Projection welding the webs to the table also is undesirably expensive because it requires complex, energy intensive and high maintenance machinery. It is therefore desirable to replace current brake shoe assembly process technology with a more reliable, flexible procedure.
This invention addresses the needs and shortcomings presented by conventional processes. This invention provides a more precise, less expensive and less labor intensive method of assembling brake shoes compared to the prior art. The method of this invention includes using a linear friction welding process to join the webs to the brake shoe table.